Pages

Tuesday, March 31, 2015

Bushmaster - due out on June 2, 2015 - is the story of one man’s obsession with an enigmatic and deadly reptile. Raymond Ditmars (1876-1942), the first curator of reptiles at New York’s world-famous Bronx Zoo, popularised cold-blooded animals as never before. His love for snakes, insects and other misunderstood creatures was conveyed in books, lectures, and pioneering motion pictures. But his expeditions to the South America jungles during the 1930s in search of the legendary bushmaster – the world’s largest viper – really captured the public imagination. In Bushmaster the author, Dan Eatherley, follows in Ditmars’s footsteps and attempts to achieve what Ditmars himself failed to do: find a bushmaster in the wild. Eighty years on, will Dan have any more luck? And will a bushmaster find him first?

Dan Eatherley is a British naturalist, writer and wildlife film-maker with a first class zoology degree from Oxford University. Dan has made a variety of natural history TV documentaries for the BBC, National Geographic, and the Discovery Channel, including credits as an assistant producer on two BBC series hosted by Sir David Attenborough: Life of Mammals and Planet Earth. He has filmed on location in swamps, deserts and jungles around the world. He has written over 100 articles on science and environmental issues for New Scientist, Scientific American and BBC Wildlife magazines. These days, when not hunting giant vipers, he works from his home in southwest England as a consultant in environmental sustainability.

Some advance reviews for Bushmaster:

“Bushmaster is a skillful work that combines the author’s own journey of discovery while shadowing the footsteps of one of the world’s most celebrated herpetologists and early pioneers for the conservation of reptiles with a fascinating history of the early evolution and modernization of the Bronx Zoo and herpetology in general.” —Austin Stevens, herpetologist, author, and adventure wildlife filmmaker

"There is perhaps no snake that so captures the imagination as the bushmaster, creature of myth, a real life dragon in serpent form. This quest to find one in the wild is a personal odyssey driven by fascination, and an intriguing read for any herpetologically minded wildlife fiends." —Steve Backshall, naturalist, writer, television presenter

"The world's greatest snakehunter, his quest for a legendary serpent, and a modernBoy's Own adventure, three stories elegantly intertwined in Bushmaster. Beautifully written and meticulously researched, I'm sure like me you won't be able to put it down." —Nigel Marven, television presenter

“A considerable number of persons can trace their interest in herpetology to days reading the many books by Raymond L. Ditmars. Those of us who have worked with bushmasters feel fortunate to have had this wonderful opportunity. Dan Eatherley has captured their essence and the nexus with Ditmars—unearthing a plethora of new information about one of our famous and most productive herpetologists.” —James B. Murphy, research associate zoologist, Division of Amphibians & Reptiles, Smithsonian National Museum of Natural History

“When I was a mere stripling my mother bought me Snakes of the World by Raymond L. Ditmars. My innate fascination for snakes soared to the skies with this book. But I never did realize what an incredible character Ditmars was. InBushmaster Dan Eatherley brings to life this enigmatic hero to uncounted, obsessed herpers.” —Romulus Whitaker, herpetologist, conservationist, and filmmaker

You can find Dan Eatherly's web page at www.daneatherley.com and his Twitter account at: @daneatherley

JUST LIKE A
COFFIN.
Five feet long, three feet wide, and three feet high, the wooden box dominates
the landing.

“The expressmen must
have had some job getting it up here,” muses the nineteen-year-old. According
to the delivery note, the sender is a “Mr.
R. R. Mole, Port-of-Spain.” After three months the consignment finally
showed up at port yesterday aboard the SS
Irrawaddy of the Trini­dad line, and just a few hours ago the crate was
delivered by horse and cart to the large brownstone house on Bathgate Avenue.
Dinner seemed to take forever but now it’s over. Insisting that his parents
remain two sto­ries below, the young man can at last get to work with hammer
and pry bar. He ignores the intermittent buzzes coming from the room adjacent
to the landing. Forcing off the lid, he prepares for the draught of fetid air,
a sure sign of a dead specimen, but is relieved to detect only a faint nutty
odor. Under several inches of brittle straw lie various large burlap sacks,
each knotted and labeled. Turning over a tag, he shudders as two words are
revealed in a neat script.

Lachesis muta

The sack expands and
contracts in response to the breathing of its contents whose rough scales press
a distinctive pattern against the fabric.

Like
the surface of a pine cone,
he thinks.

“Everything all right up
there, Ray?” his mother’s voice disturbs the youth’s reverie.

“Fine. Don’t anybody
come up!” He needs to get a move on.

Heart pounding, the
teenager grasps the bag above the knot and lifts it from the crate. It’s
disappointingly light given that Mole’s note describes an animal of “about
eight feet long.” Books and articles had led him to expect a specimen of that
length to be far heavier. Holding the sack away from his body, he enters a
small adjoining room via a door fitted with strong springs. Glass-fronted cages
are arranged in two tiers along one wall. Above them stretches the desiccated
skin of a large snake, a python maybe.

The buzzing, emanating
from one of the upper cages, intensifies. The teenager places the sack in a
large empty cage on the lower tier and loosens the knot. He reaches for a broom
handle; attached to one end is a piece of stiff wire twisted like a shepherd’s
crook. Using this, he inverts and raises the bag, hoping to coax out its tenant
from a safe distance, but the animal is not cooperating and instead braces
itself against the cloth, defying gravity. The beast does at least offer up a
glimpse of alternating salmon-pink and jet-black markings. Impatient to see
more, the young man whips away the sack with his hand, spilling the creature
out into the cage.

He would never forget
the turmoil of impressions etched on his brain in that instant: the snake’s
length far exceeding that suggested by its weight; the keeled scales lending
the skin a rasp-like quality; the waxy sheen of the animal; the blunt head;
and, set above pinkish jowls, the red­dish-brown eyes with their elliptical
black pupils. In the moments these features take to register, the front half of
the reptile’s body rises to form a huge “S” while the glistening pink tongue
forks at the air.

Then the snake advances.

In horror the teenager
backs away, knocking over a chair.

The reptile follows.

Never has he encountered
a viper actually prepared to pursue him. In his experience, even the most
venomous of snakes are cowards and, unless cornered, flee at the first sign of
trouble. With the staff he tries ever more forcefully to check the giant
reptile’s progress, attempting to lift and push it back, but the limbless body
of his adversary slides over the hook like jelly. The snake is between him and
the door, cutting off any hope of escape. The buzzing is now an uninterrupted,
deafening drone.

Downstairs his mother
drops her knitting. “That was definitely
a crash I just heard, John.”

“Relax, my dear. Ray
seems to know what he’s doing,” responds her husband with little conviction.
They both glance nervously at the ceiling.

And still the serpent
advances.

The inch-long fangs and
excessive amounts of venom for which this species is notorious dominate the
young man’s thoughts. Can this snake know its own power? Can that dancing
tongue taste his fear?

The teenager has almost
nowhere left to go when, in his peripheral vision, he notices a broom. He
flicks it behind him with the crook of his staff. Retreating another step, in
one motion he grabs the implement and shoves the bristles sharply into the face
of his pursuer. The snake pauses, pulls its body into a tight coil and beats
out a rhythm against the floor with the strange horny tip of its tail. The
youth catches his breath. Saved!

Broom in hand and more
confident, he advances on the reptile. Sev­eral additional firm jabs encourage
the serpent to turn and creep toward the cage. The teenager gently raises the
snake’s chin with his staff ena­bling the viper to glide into its new quarters.
He slams shut the glass door to the cage and slumps to the floor, gasping and
prickled by sweat.

Now for the boas.

Editor's note. Dan Eatherley spent sometime with me in Trinidad searching for bushmasters. To find out the results of his quest you will need to read the book. JCM

In a
new paper published in PLoS, Reeder et al.
(2015) note that squamate reptiles (lizards and snakes) are an important and
diverse group of terrestrial vertebrates, with more than 9,000 species and that
studies of squamate biology are presently hampered by uncertainty over their
phylogeny.

Higher-level squamate phylogeny is currently
unresolved because of conflicts between hypotheses based on separate analyses
of morphological and molecular datasets.

Most attention has focused on the
placement of iguanians (including iguanas, anoles, chameleons, dragons, and
relatives), which are placed at the base of the squamate tree in morphological
analyses, and in a clade (called Toxicofera) with snakes and anguimorphs
(including monitor and alligator lizards, the Gila monster, and relatives) in
molecular analyses. The largest morphological dataset (in characters) included
189 squamate taxa (140 living and 49 fossil; plus 3 outgroup taxa) and 610
characters (~33% missing data; Gauthier et al., GEA hereafter).

The largest
molecular dataset (in terms of characters) included 161 living taxa (plus 10
outgroup taxa) for up to 44 nuclear protein-coding loci (33,717 base
pairs/characters; ~20% missing data);
Wiens et al., (WEA hereafter). Given the unresolved conflict between these two
large datasets over the placement of Iguania, some authors have considered
higher-level squamate relationships to be unresolved. Some recent, prominent
studies have considered the traditional, morphological tree only, ignoring the
molecular hypothesis altogether.

In this study the authors perform an integrated
analyses to resolve this conflict and further elucidate the relationships of
both living and fossil squamates. First, they generated an expanded
morphological dataset with taxon sampling largely matching that of GEA for
extant taxa, adding new data from 81 additional characters (primarily from
squamation) to the mostly osteological dataset of GEA. This is a 13% increase
in characters (to 691), and the largest morphological dataset for squamates.
Next, they expanded the molecular dataset of WEA by including published
sequences from two additional loci (nuclear c-mos; mitochondrial ND2) for
closely matched species yielding up to 46 protein-coding loci and 35,673
characters for each of 161 taxa. We then performed separate and combined
analyses of each dataset using likelihood, Bayesian, and parsimony approaches,
and evaluated the potential causes of conflict by examining trees from subsets
of the molecular and morpohological data. Combined analyses included
reweighting the molecular data such that genes were treated as equivalent to
morphological characters.

The results
resolve higher-level relationships as indicated by molecular analyses, and
reveal hidden morphological support for the molecular hypothesis (but not
vice-versa). Furthermore, the authors find that integrating molecular,
morphological, and paleontological data leads to surprising placements for two
major fossil clades (Mosasauria and Polyglyphanodontia), demonstrate the
importance of combining fossil and molecular information, and the potential
problems of estimating the placement of fossil taxa from morphological data
alone. These results caution against estimating fossil relationships without
considering relevant molecular data, and against placing fossils into molecular
trees (e.g. for dating analyses) without considering the possible impact of
molecular data on their placement.

The combined analyses strongly suggest
that the phylogenetic hypothesis for living squamates based on the molecular
data is correct. Specifically, the results support the hypothesis that Iguania
is placed with snakes and anguimorphs, and not at the squamate root (as
suggested by morphological data alone). The conclusions are based on several
lines of evidence, including: (a) combined analyses of the relevant molecular
and morphological data supports the molecular placement of Iguania, even when
the molecular dataset is reduced to only 63 characters, less than one tenth the
size of the morphological dataset, (b) mapping morphological characters on the
combined-data tree shows that there is actually hidden support for the
molecular hypothesis in the morphological data (similar to the number of
characters supporting the morphological hypothesis), (c) the morphological
dataset is dominated by misleading phylogenetic signal associated with
convergent evolution of a burrowing lifestyle and associated traits, and a
similar problem associated with feeding modes may explain the morphological
placement of Iguania, and (d) the morphological hypothesis is unambiguously
supported by only one of six subsets of the morphological data. Conversely, we
find no evidence for hidden signal supporting the morphological hypothesis
among the 46 genes in the molecular dataset; no genes support this hypothesis.
Further, the failure of some genes to fully support the molecular placement of
iguanians in Toxicofera seems to be associated with sampling error (i.e.
shorter genes).

Sunday, March 29, 2015

The invasive Burmese python (Python molurus bivittatus or Python bivittatus) has been suspected in
the drastic decline of mammal populations in Everglades National Park (ENP)
over the last several decades, The park is globally recognized for its unique
biotic communities, sits at the southern end of the Greater Everglades
Ecosystem (GEE), a vast freshwater wetland (≈10 000 km2) encompassing most of
the southern Florida peninsula. The ecological processes, functionality and restoration
efforts within this distinct ecosystem are probably being substantially
impaired by the disappearance of once common mammalian predators and herbivores.
Declines in mammal populations in ENP appear to coincide temporally and
spatially with the arrival and spread of invasive Burmese pythons, a
large-bodied snake native to Southeast Asia that preys on vertebrates. Pythons
were probably introduced into ENP several decades ago via releases or escapes
from private ownership. Sightings and removals of pythons in ENP were sporadic
in the 1980s and 1990s, and increased sharply in the early 2000s. During this
time, gut content analysis of invasive pythons in ENP indicated that mammals
accounted for about 75% of their diet.

Previous evidence linking pythons
to mammal declines has been indirect, and there are reasons to question whether
pythons or any predator could have caused the precipitous declines seen across
a range of mammalian functional groups. Introduced predators, including snakes,
have reduced or eliminated fauna on islands, yet there are no accounts of a
lone introduced apex predator (apart from humans) removing a functionally
diverse, continental mammal community. Additionally, ecological theory provides
little support for the hypothesis that an apex predator could extirpate small,
broadly dispersed, fecund, generalist herbivores.

In a new article in the Proceedings of the Royal Society of London
B: Biological Sciences McCleery et al.
(2015) test the hypothesis that pythons are driving the decline of mammal
populations, and they experimentally manipulated the marsh rabbit (Sylvilagus palustris) populations in
ENP.

Marsh rabbits are small (≈1 kg)
lagomorphs found near fresh and brackish water throughout the southeastern USA.
They are sexually active throughout the year and can produce up to six litters of
three to five young annually. Through the 1980s, this species was one of the most
commonly seen mammals in ENP. Despite having a wide variety of natural
predators, marsh rabbits are still common in areas of the GEE outside of ENP.
For these reasons, and because rabbit populations are generally resilient and
capable of persisting under considerable predation pressure the authors chose marsh rabbits as a model to understand
the impacts of pythons on mammals in ENP. If pythons caused the declines of
marsh rabbits in ENP, they predicted that (i) pythons would be the dominant
cause of marsh rabbit mortality in ENP, (ii) mammals would cause more marsh
rabbit mortalities in areas of the GEE where pythons were rare or absent, (iii)
marsh rabbit populations introduced in ENP would not persist, and (iv) unlike
endothermic predators (i.e. mammals), the timing of python-caused mortality
would vary with seasonal climate conditions.

The authors experimentally
manipulated the marsh rabbit populations to determine the role of pythons in
driving mammal declines within ENP. They compared the risk of mortality from
different causative agents in areas with established Burmese python populations
to similar areas where pythons were rare or absent. The also evaluated the
influence of environmental factors on temporal variation in mortality rates
from the dominant predators of marsh rabbits (e.g. pythons and mammals) in the
GEE.

They captured marsh rabbits from
donor populations and randomly assigned them to one of three sites: two sites
in ENP and a procedural control site in the GEE, where pythons had not been
observed. The purpose of the procedural control was to account for the
influence of translocation on mortality events. The also established a control
site where pythons were rare or absent to compare causes of mortality in ENP
with an established population of marsh rabbits that was not manipulated. At
the control site, they captured and released rabbits without trans-locating
them.

They captured, released and
radiotracked 95 adult marsh rabbits from 14 September 2012 to 19 August 2013
(coastal ENP = 15, freshwater ENP = 16, procedural control = 15, control = 49).
Eighty rabbits survived the 10-day adjustment period needed to reduce
exploratory movements and acclimate to the sites. Additionally, 10 rabbits were
censored after the 10-day adjustment period (e.g. lost signal from predation or
equipment failure), and two rabbits were alive at the end of the study, so the
study documented 68 rabbit mortalities. Classification of the cause of
mortality for 55 rabbits was possible and the remaining 13 rabbit mortalities were
listed as being from an unknown endothermic predator. Marsh rabbits in ENP
faced the greatest risk of predation from pythons, which accounted for 77% of
all mortalities. And, the authors attributed only one rabbit mortality in ENP
to mammal predation. This was in stark contrast to results from control sites,
where no rabbits were killed by pythons and they attributed 71% of classified
mortalities to mammals. Only three rabbits (8%) at the control site were eaten
by snakes, all native eastern diamondback rattlesnakes (Crotalus adamanteus).

The loss of marsh rabbits and other
mammals from ENP is probably causing a
massive rearrangement of the ENP food web, losses in ecosystem function, and
complex and unpredictable cascading effects. As prey and predators at multiple
trophic levels, nutrient cyclers and engineers of vegetation, mammals are an
indispensable component of the GEE. This research clearly establishes pythons
as a causal agent of marsh rabbit declines, a species selected because of its
theoretical resilience to predation pressure. Accordingly, pythons are a
logical and likely explanation for the observed declines in less fecund
mammalian prey found in ENP (raccoon, round-tailed muskrat, bobcat).

Only with the recovery of the parks
mammal populations will it be possible to restore the health and functionality
of this World Heritage Site. However, it seems unlikely that marsh rabbits and
other mammal populations will rebound without action to manage pythons. Because
pythons are capable of persisting in the environment by switching to different
prey and going long periods without food controlling them is a difficult
challenge. Without effective tools and a strategy for reducing the prevalence
of these invasive snakes, the dire state of mammals in the Everglades will
probably remain unchanged, and spread if python populations expand northward or
become established elsewhere in the USA.

Saturday, March 28, 2015

A previously
undiscovered species of crocodile-like amphibian that lived during the rise of
dinosaurs was among Earth's top predators more than 200 million years ago.

Paleontologists
identified the prehistoric species -- which looked like giant salamanders --
after excavating bones buried on the site of an ancient lake in southern Portugal.
The species was part of a wider group of primitive amphibians that were
widespread at low latitudes 220-230 million years ago, the team says.

The creatures grew up
to 2m in length and lived in lakes and rivers during the Late Triassic Period,
living much like crocodiles do today and feeding mainly on fish, researchers
say.

The species -- Metoposaurus algarvensis -- lived
at the same time as the first dinosaurs began their dominance, which lasted for
over 150 million years, the team says. These primitive amphibians formed part
of the ancestral stock from which modern amphibians -- such as frogs and newts
-- evolved, researchers say.

The species were
distant relatives of the salamanders of today, the team says. The discovery
reveals that this group of amphibians was more geographically diverse than
previously thought.

The species is the
first member of the group to be discovered in the Iberian Peninsula, the team
says.

Fossil remains of
species belonging to the group have been found in parts of modern day Africa,
Europe, India and North America. Differences in the skull and jaw structure of
the fossils found in Portugal revealed they belong to a separate species.

The new species was
discovered in a large bed of bones where up to several hundred of the creatures
may have died when the lake they inhabited dried up, researchers say. Only a
fraction of the site -- around 4 square meters -- has been excavated so far,
and the team is continuing work there in the hope of unearthing new fossils.

Most members the
group of giant salamander-like amphibians was wiped out during a mass
extinction 201 million years ago, long before the death of the dinosaurs. This
marked the end of the Triassic Period, when the supercontinent of Pangea --
which included all the world's present-day continents -- began to break apart.
The extinction wiped out many groups of vertebrates, such as big amphibians,
paving the way for dinosaurs to become dominant.

The study, published
in the Journal of Vertebrate Paleontology, was funded by the German
Research Foundation and the National Science Foundation, the Jurassic
Foundation, CNRS, Columbia University Climate Center and the Chevron Student
Initiative Fund. Additional support was provided by the Municipality of Loulé,
Camara Municipal de Silves and Junta de Freguesia de Salir in Portugal.

Dr Steve Brusatte, of
the University of Edinburgh's School of GeoSciences, who led the study, said:
"This new amphibian looks like something out of a bad monster movie. It
was as long as a small car and had hundreds of sharp teeth in its big flat
head, which kind of looks like a toilet seat when the jaws snap shut. It was the
type of fierce predator that the very first dinosaurs had to put up with if
they strayed too close to the water, long before the glory days of T. rex and Brachiosaurus."

Dr Richard Butler, of
the School of Geography, Earth and Environmental Sciences at the University of
Birmingham, said: "Most modern amphibians are pretty tiny and harmless.
But back in the Triassic these giant predators would have made lakes and rivers
pretty scary places to be."

Dr Steve Brusatte
will discuss his work on recently discovered species and other aspects of paleontology
at a series of events at the Edinburgh International Science Festival, which
runs from 4-19 April.

Citation

Brusatte
SL, Butler RJ, Mateus Steyer JS. A new species of Metoposaurus from the Late Triassic of Portugal and comments on the
systematics and biogeography of metoposaurid temnospondyls. Journal of
Vertebrate Paleontology, 2015; e912988 DOI:10.1080/02724634.2014.912988

The
Asian family Xenodermatidae includes five genera: Xenodermus Reinhardt, 1836 (1
species), Achalinus, Fimbrios, Stoliczkaia, and Xylophis,
and hold a total of 17 species. The Philippine genus Oxyrhabdium has been removed from the family based on molecular evidence,
nevertheless, its phylogenetic position should be further investigated as it is
now classified as Elapoidea incertae
sedis. This family has long been considered to be a subfamily of the
Colubridae. Recent phylogenetic studies suggest this well-defined assemblage
deserved family status. These genera include species with more or less highly
modified cephalic (labials with raised and everted edges, presence of ridges of
skin between rostral and internasals, and a large loreal) and dorsal scalation
(usually small scales, subequal or intermixed with large scales). The
Neotropical genus Nothopsis Cope,
1871, previously also referred to the family Xenodermatidae, but was
transferred to the family Dipsadidae and the members of Xenodermatidae are
currently known only from Asia, ranging from India eastward to Japan and
Taiwan, and southward to Borneo and Java, possibly also the Philippines.

Malcom
Smith erected the monotypic snake genus Fimbrios
for Fimbrios klossi, and described it
from Da Lat, Langbian Plateau in southern Vietnam in 1921. This species was
subsequently recorded from the Elephant Mountains, in southwestern Cambodia,
and from central and southern Vietnam. Although it has been recorded close to
the Laotian border, it was not recorded from the Laos until 2008, when a
specimen was collected in the Paksong District, Champasak Province, in Boloven
Highlands. Two additional specimens, found in 2007 and 2008 in the same
locality of the Boloven Highlands between 1,320 and 1,340 m asl. Fimbrios smithi was described in 2008 on
the basis of a specimen obtained in the karst forest of Phong Nha—Ke Bang
National Park, Quang Binh Province, in central Vietnam.

In a new paper Teynié et al. describe a new genus and species of xenodermatid snake from
Laos based upon a specimen collected during a trip in the northern part of
Louangphabang Province, which presented several diagnostic characters of the genus
Fimbrios. The male snake and a second specimen observed in Houaphan Province,
North Laos, share morphological characters with the Asian genus Fimbrios including erected edges on the
first supra and infralabial scales, but differ in having fewer dorsal scale
rows (25–27 vs. 30–33), fewer maxillary teeth (27 vs. 30–35), posterior teeth
progressively slightly enlarged, and especially the correspondence of two
dorsal scale rows per ventral plate throughout the body (i.e. the first dorsal
scale row made of a small scale above the fore part of a ventral, followed by a
much larger scale above its hind part), a condition known only in Xenodermus Reinhardt, 1836.

As
the Laotian specimens differ in morphological and molecular characters from
other xenodermatids, Teynié et al
placed these specimens in a new genus, Parafimbrios
and describe them as Parafimbrios lao.
Besides the characters mentioned above, the new species is diagnosed by a
combination of the following ones: small, strongly keeled dorsal scales;
rostral and first four supra- and infralabials with raised, erected edges;
horizontal tissue ridges above the rostral; loreal single, large, elongate;
ventral scales 177–189; subcaudals 55–56, undivided; dorsal color
purplish-grey, neck with a broad, very pale grey collar reaching downwards the
pale grey color of the venter. Parafimbrios
laos is the 111th snake species recorded from Laos.

The
holotype was discovered in a steep, rocky evergreen forest, with some trees of
primary forest remaining, surrounding a rugged karst formation. The holotype
was found lying motionless at night during the rainy season on a rocky outcrop
among a large pile of rocks at the foot of a limestone cliff of the karst
formation at an elevation of 360 m. The adjacent lowland is mainly covered with
rice fields, patches of secondary forests and a few scrub and grasslands. The
second specimen was observed near the city of Vieng Xai, where no large primary
forest remain. This specimen was observed in the same general karstic
environment as the holotype. Neither specimen displayed any reaction and
remained perfectly motionless when they were photographed. When they were
handled, they did not try to form a “ball”, a defensive posture frequent in Fimbrios klossi, nor did they display
any other defensive action. Nothing else is known on the biology of Parafimbrios lao, stomachs of both
specimens were empty.

Thursday, March 12, 2015

Here are the articulated cranium and lower jaws shown in oblique right lateral view (A). Right facial skeleton and skull roof shown in "exploded" view to illustrate the nature of sutural contacts (B); the left side of the cranium (braincase omitted) is shown in internal view (C). The right lower jaw in "exploded" view to illustrate sutural morphology. Individual bones shown in various colors.Artist Credit: Porro et al..

The
first 3D reconstruction of the skull of a 360 million-year-old near-ancestor of
land vertebrates has been created by scientists from the Universities of
Bristol and Cambridge, UK. The 3D skull, which differs from earlier 2D
reconstructions, suggests such creatures, which lived their lives primarily in
shallow water environments, were more like modern crocodiles than previously
thought.

The
researchers applied high-resolution X-ray computed tomography (CT) scanning to
several specimens of Acanthostega gunnari,
one of the 'four-footed' vertebrates known as tetrapods which invaded the land
during one of the great evolutionary transitions in Earth's history, 380-360
million years ago. Tetrapods evolved from lobe-finned fishes and display a
number of adaptations to help them survive on land.

An
iconic fossil species, Acanthostega
gunnari is crucial for understanding the anatomy and ecology of the
earliest tetrapods. However, after hundreds of millions of years in the ground
fossils are often damaged and deformed. No single specimen of Acanthostega preserves a skull that is
complete and three-dimensional which has limited scientists' understanding of
how this key animal fed and breathed -- until now.

Using
special software, the Bristol and Cambridge researchers 'digitally prepared' a
number of Acanthostega specimens from
East Greenland, stripping away layers of rock to reveal the underlying bones.

They
uncovered a number of bones deep within the skull, including some that had never
before been seen or described, resulting in a detailed anatomical description
of the Acanthostega skull.

Once
all of the bones and teeth were digitally separated from each other, cracks
were repaired and missing elements duplicated. Bones could then be manipulated
individually in 3D space. Using information from other specimens, the bones
were fitted together like puzzle pieces to produce the first 3D reconstruction
of the skull of Acanthostega, with
surprising results.

Lead
author, Dr Laura Porro, formerly of Bristol's School of Earth Sciences and now
at the Royal Veterinary College, said: "Because early tetrapods skulls are
often 'pancaked' during the fossilization process, these animals are usually
reconstructed having very flat heads. Our new reconstruction suggests the skull
of Acanthostega was taller and
somewhat narrower than previously interpreted, more similar to the skull of a
modern crocodile."

The
researchers also found clues to how Acanthostega
fed. The size and distribution of its teeth and the shape of contacts between
individual bones of the skull (called sutures) suggest Acanthostega may have initially seized prey at the front of its
jaws using its large front teeth and hook-shaped lower jaw.

Co-author,
Professor Emily Rayfield, also from Bristol's School of Earth Sciences, said:
"These new analyses provide fresh clues about the evolution of the jaws
and feeding system as the earliest animals with limbs and digits began to
conquer the land."

The
researchers plan to apply these methods to other flattened fossils of the
earliest tetrapods to better understand how these early animals modified their
bones and teeth to meet the challenges of living on land.

Digital
models of the original fossils and the 3D reconstruction are also useful in
scientific research and education. They can be accessed by researchers around
the world, without risking damage to fragile original fossils and without
scientists having to travel thousands of miles to see original specimens.
Furthermore, digital models and 3D printouts can be easily and safely handled
by students taking courses and by the public during outreach events.

Wednesday, March 11, 2015

Many chameleons have the remarkable ability to make
rapid and complex color changes in their social interactions. In a
collaboration between biology sections researchers and physics at the Faculty
of Science of the University of Geneva (UNIGE) results in the discovery of the
mechanisms governing the phenomenon. In the study published by Nature Communications, the group co-led
by Professors Michel Milinkovitch and Dirk van der Marel demonstrates that the
changes occur through the active control of a nano-crystal mesh present in a
surface layer of skin cells, the iridophores. The researchers also testify
to the existence of a deeper layer of iridophores, whose crystals, bigger and
less organized, reflect infrared light. Such a superposition of two
different types of iridophores is new in evolutionary terms; it is what
allows chameleons spend an effective camouflage a spectacular parade in record
time; is that it also provides a passive thermal protection to the animal.

The colorful adornments that turn at the discretion of
the popularity of behavior are male chameleon. While the mechanisms of
change to a darker hue are known, those that govern the transition from a
bright color to another flamboyant tone remained mysterious. Some species,
such as the panther chameleon, for example, are able to make such a transition
in one to two minutes, to woo a female or face another male.

The blue color of the chameleon structural
Besides brown pigments, red and yellow, chameleons and other reptiles have
called structural colors. "These colors are actually created without
pigments, via an optical interference phenomenon. They derive from
interactions between certain wavelengths and nanoscopic structures such as tiny
crystals in the skin of reptiles, "says Michel Milinkovitch, professor at
the Department of Genetics and Evolution of the University of Geneva.These
nanocrystals are arranged in alternate layers with the cytoplasm in iridophores
named cells. Millefeuille formed selectively reflects certain wavelengths
and this phenomenon contributes to the flamboyant colors many reptiles.

To determine how is the transition from a colorful
adornment to another in the panther chameleon, researchers from two
laboratories of the University of Geneva have worked hand in hand, combining
the skills of experts in quantum physics and biology of evolution. "We
found that the animal can change color by active adjustment of nanocrystals
mesh. When the chameleon is calm, they are organized into dense network
and reflect the lengths of blue waves. But the excitement causes release
within iridophores of the animal and allows reflection of other colors, such as
yellow or red "explain Jeremiah Teyssier physicist and biologist Suzanne
Saenko, who are the co-first authors of the article. The set is a unique
example of self-organized optical system controlled by the animal wearing it.

Crystals as heat shield
Scientists have also demonstrated the existence of a second layer of
iridophores, deeper. "These cells, which contain larger crystals and
less organized, reflect a significant proportion of infrared wavelengths,"
explains Michel Milinkovitch. This layer acts as a very effective
protection against thermal effects due to exposure to the sun in low latitudes.

Furthermore, in terms of evolution, the organization
of iridophores two layers is a novelty that allowed the passage chameleons in
record time for an effective camouflage a spectacular parade, while providing
thermal protection passive.

The researchers now intend to explore the cellular
mechanisms that govern in the iridophores, change nanocrystals mesh, as well as
the development of crystalline layers.

Search This Blog

Bush Maco Trinidad & Tobago

A place to document your Trinidad & Tobago Nature Observations

Cookies

We do not use device identifiers to personalise content, ads, nor provide social media features or analyse our traffic. Thus we do not share such identifiers or other information from your device with social media, advertising and analytics partners.